SOLUTION: sorry gave wrong address before...a motorist drives 450 miles in 8 hours. on the journey he averages 60 mph before noon and 50 mph after. what were his departure and arrival times?

Question 237116: sorry gave wrong address before...a motorist drives 450 miles in 8 hours. on the journey he averages 60 mph before noon and 50 mph after. what were his departure and arrival times? i used formula d=rt, d=450. i know i don't add the 2 rates, but do i average the averages to solve for t (r=55) , 8.01 ...wrong! i also found the average travel time for the whole trip is 56.25 mph ...doesn't help. how do i solve for t?
450=60 t + 50 t???
thanx for reading
Found 2 solutions by Alan3354, rfer:
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
sorry gave wrong address before...a motorist drives 450 miles in 8 hours. on the journey he averages 60 mph before noon and 50 mph after. what were his departure and arrival times? i used formula d=rt, d=450. i know i don't add the 2 rates, but do i average the averages to solve for t (r=55) , 8.01 ...wrong! i also found the average travel time for the whole trip is 56.25 mph ...doesn't help. how do i solve for t?
450=60 t + 50 t???
---------------
t = time driving 60
450 = 60t + 50*(8-t)
450 = 60t + 400-50t
50 = 10t
t = 5 hours
1200 - 500 = 0700 departure
---------------------
0700 + 800 = 1500 arrival (= 3 PM)

Answer by rfer(16322) (Show Source): You can put this solution on YOUR website!
total time is 8 hrs
the ratio is 5/6
8:22 am
4:22 pm

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